Manufacture of succinic acid



, liberate hydrogen and which Patented Feb. 27, 1945 Elton same, Buffalo, N. Y., assignor to Allied Chemical 8t Dye CorporatiomNew York, N. Y., a corporation of New York No Drawing. Application September 30-, 1942, Serial No. 460,327

11 Claims. (Cl. 260537) This invention relates to a process for the manufacture of succinic acid. vIt relates more particularly to the manufacture of succinic acid from fumaric acid;

Fumaric acid is obtained asa by-product in the manufacture of other organic products. For example, it is recovered as a by-product in the manufacture of maleic anhydride. Accordingly. it provides an accessible source for the manufacture of succinic acid; but owing to its low solu- This result is surprising in view of the-low soluf bility of fumaric acid in water and in view of the disclosure in the Reid Patent 2,141,406 that, in the process of the patent for making succmlc acid from maleic acid, fumaric' acid is produced as an undesired by-product in the course of the reaction of certain metals with aqueous solutions of maleic acid.

bility in water, it has not been employed for this purpose.

It has been proposed heretofore to manufacture succinic' acid by reacting salts of fumaric acid in aqueous solution with hydrogen in the presence of a hydrogenation catalyst. Such processes, however, require the preparation of a hydrogenation catalyst and use of special pressure equipment for efficient operation, and involve the inconvenience and explosion hazards attendantupon manipulation of gaseous hydrogen under ressure.

It has alsobeen proposed by E. E. Reid in U. S. 'P. 2,141,406 to manufacture succinic acid by reacting maleic acid in aqueous solution with the metals standing between hydrogen and the alkaline earth metals in the E. M. F. series. This process requires the use of maleic acid, and while it would be possible to first convert fumaric acid to maleic acid as a preliminary step to the production of succinic acid, such a procedure would be uneconomica] and diflicult to carry out..

It is the principal object of the present invention to provide a process for the manufacture of succinic acid from fumaric acid which is simple to carry out, convenient to operate, and which In the practice of the process of the present invention in accordance with one method of procedure, fumaric acid is suspended in water and one of the metals above mentioned is added to the suspension, preferably in a highly reactive form. A reaction occurs with evolution of heat.

Upon completion of'the addition of the metal, a

non-oxidizing acid of the type referred to above is added to the reaction mixture, preferably while maintaining the reaction mixture at an elevated temperature which for convenience does not exceed the boiling point of the reaction mixture.

When the reduction has been completed, the succinic acid is recovered from the resulting reaction mixture. Ordinarily this is accomplished by removing from the hot solution of succinic acid, resulting from the reaction, insoluble material which may be present therein (for example, un-

reacted metal, unreduced fumaric acid, salts formed in the reaction, etc.), cooling ,the result-( ing clarified solution to effect crystallization of produces succinic acid directly from fumaric acid while avoiding the disadvantages'inherent in the known processes. Other objects of the invention willfin part be obvious and will in part appear hereinafter.

I have discovered .that when fumaric acid, suspended in an aqueous medium, is treated with certain metals and certain acids, succinic acid is produced in satisfactory yields for commercial application.

.Thus I have discovered that succinic acid can be produced by adding any one or' more of the metalszinc, aluminum, chromium, tin and magnesium to an aqueous suspension of fumaric acid, followed 'by the addition of a non-oxidizing acid which is capable of reacting with the metal to is sufliciently stronger than succinic acid to liberate succinic acid from a succinate of such metal.

lio

succinic acid, and separating the succinic-acid crystals from the mother liquor.

Preferably the temperature conditions, concentrations, choice and nature of reagents and the manner of their incorporation are controlled-with a view to securing a maximum yield under conditions of economical operation. Thus, the fumaric acid is suspended in an amount of water which is approximately just enough to form,.'at the elevated temperatures employed, a saturated solution of the succinic acid produced; so that upon completion of the reduction, succinic acid may be recovered in economical amounts by direct crystallization from the resulting solution,

5' preferably after separation of insoluble contamin'ants when present. In general from about 2 to about 4 parts by weight of water per part of fumaric acid fulfill this condition.

' tion mixture.

' form of powder.

The metal is preferably employed in a form adapted to. react advantageously with the fumaric of the metal is \used.)

greater activity thereof. The amount of metal used is advantageously approximately the amount theoretically required to reduce the amount of fumaric acid employed to Succinic acid. In the interest of economy and in order to produce high yields of succinic acid, the quantity of metal employed is preferably slightly in ciently concentrated or saturated with reference to succinic acid, the latter may be crystallized excess of that theoretically required to reduce the fumaric acid to succinic acid. An excess, for instance, of about 5% over the theoretically required amount has been found suitable.

Of the metals found suitable for the reaction of the invention enumerated above, it has been found that zinc and aluminum produce the highest yields of succinic acid based on the weight of fumaric acid initially employed for the process.

These metals are therefore preferred.

The acids which are suitablefor the reaction are water-soluble non-oxidizing acids, strong enough to liberate succinic acid from a succinate of the metal employed for the reduction. In

' general suitable acids are those which are at least as strong as formic acid. e. g., having a dissociation constant of at least l0 at about 25 C. Examples of such acids are formic, chloracetic, malic, citric, oxalic, phosphoric, sulfuric and hydrochloric acids. Those acids which form water-soluble salts of the metal employed in the reduction are in general preferred. Strong acids such as sulfuric acid and hydrochloric acid are especially suitable. The acid is advantageously employed in approximately the amount theoretically required for complete reaction with the amount of metal used. Preferably it is slightly more than the chemical equivalent of the-amount of metal used for the reaction; for instance, an excess of about 5% has been found desirable.

In general, the reaction is carrie'dout at an elevated temperature.

For simplicity of operation, avoiding use of pressure or reflux apparatus, temperatures between about 85 C. and the a boiling point of the reaction mixture are em:

bloyed. v l 3 Thus, in the preferred practice of the present invention, fumaric acid is suspended in an amount of water approximately equal to that required to form, at about 85 C., a saturated solution of an equivalent amount of. succinic acid,-.

and zinc or' aluminum in finely divided form is added to the agitated suspension .in portions, while-maintaining the temperature at 85 to 90 C. Before use, the metal is assayed for its re-' duction activity (1. e., its equivalence to hydrogen which it can generate with mineral acid) and an amount of the metal is used which centrifuging. V The invention will be more readily understood from the following examples, in which parts are by weight and temperatures. are expressed in 1 contained inthe aqueous portion of the reaction mixture is then recovered by any suitable procedure. For instance, if the solution is sufliby cooling, and separated from the mother liquor in substantially pure form, e. g., by filtration or tain the-temperature at about 90, with external cooling if necessary. After all of the zinc dust has been added, 358 parts (3.4 mols) of 66 Be. sulfuric acid are added at such a rate that substantially =no hydrogen gas is evolved, while maintaining the temperature between about 85 and about 90. I

requires about two hours. To the resulting mix- The addition of the acid ordinarily ture, 8' parts of decolorizing charcoal (e. g., Darco, Norit, etc.) are added, and the mixture is heated with agitation for about one hour at a temperature of. about 95 to about 100. The reaction mixture is then filtered while not Jand the filtrate is cooled to a temperature between about 20 and about Succinic acid. which crystallizes from the filtrate, is separated by filtration or centrifuging from the mother liquor. The crystalline massis washed successively with 5 portions of water of 200 parts each,

and the washed crystalline mass is dried in an atmospheric drier at about 100.

The dry succinic acid recovered contains about 98.9% succinic acid, 0.5% fumaric acid, and 0.13% ash, and is substantialli free from heavy metals.

Yields equivalent to about 90% of theory based on the total amount of fumaric acid employed have 'been obtained by this procedure. The wash is necessary theoretically to generate about 2.1 atoms of nascent hydrogen per molecule of fumaric acid used. tion activity of the metal is found to be less than 100%, .a proportionately larger amount has been added, the mixture is agitated, and

- the acid to be used is added in portions at such a rate that excessive or substantial liber-T ation of free hydrogen is avoided, while maintaining the temperature below the boiling. point of the mixture. After addition of the acid.

the temperature is maintained at the .desired The hot aqueous solution is separated, e. g., by

water may be used in making up the fumaric acid slurry for subsequent reductions, thereby avoiding loss of the succinic acid contained therein.

Example 2.-348 parts (3 mols) of purified fumaric acid are suspended in 1200 parts of water and 57 parts (2.11 mols) of powdered aluminum are added to the mixture at such a rate that the temperature does not rise substantially above 85. 358 parts (3.4 mols) of .66" B. sulfuric acid I are introduced while maintaining the tempera- (It is noted, if the-reduc- After allthe metal- I level until the reaction is substantially complete.

filtration, from the water-insoluble constituents of the reaction mixture (including, for example. unreacted metal, and in some cases. unreduced fumaric acid and insoluble salts of. the metal used for the reduction) andthe succinic acid ture of the mixture at to the addition of the acid requiring approximately two hours. The resulting mixture is heated for about one hour to a temperature between and and is'then filtered. The filter cake con-.

sists mainly of unreacted aluminum. Upon cooling the fllltrate to about 25, aslurry of succinic .acid crystals-is obtained. The slurry is filtered, and the crystalline filter cake is washed and dried as in the preceding example.

The product thus recovered contains 95% suc-- cinic acid and 4.6% fumaric acid? I Emmple {i -To a slurry of 348 parts (3 mols) oi purified fumaric acid,- suspended in 1200 parts of water," parts of powdered chromium (2.1.1 mols) are added at such a rate that the temperature does not rise above about 85. The mixtureis then heateii to boiling and 358 parts of 66 example.

B. sulfuric acid are added drop-wise. An exceedingly vigorous reaction takes place. Upon completion of the reaction, the mixture is worked up in the same manner as in the preceding example. A crystalline product containing 92.4% succinic acid and 7.5% fumaric acid is obtained.

It has been found that chromium does not 66.7% succinic acid and 32.1% fumaric acid.

Example 5.-A slurry of fumaric acid'is reduced by the process of Example 2 but substitut-' ing 77 parts (3.17 mols) of magnesium chips and turnings for the powdered aluminum used in said On working up the reaction mixture by the procedure of Example 2, a crystalline mass containing about 50% succinic acid and 50% fumaric acid is obtained. I

Example 6.A chemically equivalent quantity of hydrochloric acid is substituted for the sulfuric acid used in the procedure of Example. 5. The crystalline product obtained in this case contains about 45% succinic acid and about 55% fumaric acid.

In Examples 5 and.6, relatively lower yields of succinic acid are obtained as compared with Examples 1. and 2, apparently as a result of the react appreciably at temperatures below about 97 while above thistemperature the reaction excessive reactivity of the magnesium, whereby control of the liberation of hydrogen is rendered relatively difficult, resulting in losses of hydrogen.

Example 7.-A slurry of fumaric acid is re duced with zinc dust in the manner described in Example 1, substituting an equivalent amount of formic acid for the sulfuric acid employed in said example. Upon workin up the reaction mixture by the procedure set forth in Example a crystalline product containing-61% succinic acid, 2.5% fumaric acid, and'22.5% zinc (in the form of its salts) is obtained. The filter cake separated from the hot reaction mixture in the course of the clarification thereof consists main"- 1y of unreacted zinc together with a small amount of succinic acid and fumaric acid.

Example 8.Fumaric acid is reduced withminc dust in the manner described in Example 1, but

dust as described in Example 1, but substituting an equivalentamount of malic acid for the sulfuric acid employed in said example. The results are similar to those obtained in the preceding example.

3 Example 10.--An aqueous slurry of fumaric acid is reduced with active zinc in the manner describedin Example 1, substituting an equiva-.

lent amount of phosphoric acid for the sulfuric phates is separated. The crystalline product. re-

covered from the filtrate contains 70% succinic acid and 30% fumaric acid.

Example 11.--Fumaric acid is reduced by a l process similar to that of Example 1, substituting an equivalent amount of oxalic acid for the sulfuric acid used in said example. The filter cake obtained upon filtration of the hot reactionmixture contains unreacted zinc and insoluble zinc'oxalate; The crystalline product recovered from the filtrate contains about 96% succinic acid and about 4% fumaric acid.

Eaample 12.-Fumaric acid is reduced with zinc dust in a procedure similar to that of the preceding example, substituting an equivalent amount of citric acid for the oxalic acid used in said example. The filter cake' obtained upon filtration of the hot reaction mixture consists almost entirely of zinc citrate, and'the crystalline product recovered upon cooling the filtrate contains 85% succinic acid and 15% fumaric acid. v

The best yields are obtained by using powdered zinc or aluminum with a strong non-oxidizing mineral acid, particularly sulfuric acid. Relatively lower yields are obtained in the case of magnesium, apparently as there's-ult of the greater reactivity of this. metal, compared with zinc and aluminum. In the case of tin, yields are lowor apparently as the result of the lower reactivity of this metalunder the above reaction conditions: while with chromium relatively low yields appear to be due to the peculiar sensitivity of this metal under the conditions of the reaction to the temperature employed. Thus, zinc and aluminum appear to possess the optimum degree of reactivity, especially for use with the preferred mineral acids and under the preferred operating conditions.

The use of acids which are Weaker than sulfuric acid, while effective for the purposesTof the reaction, results in relatively lower yields of succinic acid. Formic acid used inExample 7 is effective for the reduction, but is not strong enough talline product recovered. Thus, in order to obtain succinic acid substantially uncontaminated with salts the o it is desirable to use acids stronger than 0 '0 acid. Strong mineral acids are preferred. Pho phoric, oxalic and citric acids generally produce nsoluble salts of the metals employed for the reduction; hence for preferred operation they are not employed in the interest of technical convenience.

acid used in said example. Upon filtration of the 4 hot reaction mixture, a' filter cake consisting mainly of unreacted zinc and insoluble zinc-phos- Variations and modifications may be made 'within the scopeof this invention; hence, the details of the foregoing examples are to be interpreted in an illustrative rather than a limiting sense.

Iclaim:

1. A process for the manufacture of succinic acid, which comprises mixing fumaric acid in an aqueous medium with ametal-selected from the ,class consisting of zinc, aluminum, chromium, tin, and magnesium, and adding to the resulting mixture a non-oxidizing acid which is capable of reacting with the metal to liberate hydrogen and which is sufficiently stronger than succinic acid to liberate the latter from a succinate of the metal, said non-oxidizing acid being added in at least the amount theoretically required to react with the amount of metal employed.

' 2. A process for the manufacture of succinic acid, which comprises mixing an aqueous suspension of fumaric acid with a metal selected from the class consisting of zinc, aluminum, chromium.

tin, and magnesium, in a form presenting an extended surface accessible to the reaction mixture.

and adding to the resulting mixture a non-oxidizing acid which is capable of reacting with the metal toliberate hydrogen and which has a dissociation constant of at least 1(ir at C., said non-oxidizing acid being added in at least the amount theoretically required to react with the amount of metal employed.

3. A process for the manufacture of succinic acid, which comprises mixing fumaric acid in an aqueousmedium with a finely divided metal selected from the class consisting of zinc, aluminum, chromium, tin, and magnesium, at least in the amount theoretically required for the reduction ofthe fumaric acid and adding to the resulting mixture a strong non-oxidizing mineral acid adapted to form a water-soluble salt of the metal employed for the reduction, said non-ox-' idizing acid being added in at least the amount theoretically required to react with the amount of metal employed.

4. Aprocess for the manufacture of succinic acid, which comprises mixing a finely divided metal selected from the class consisting of zinc,

aluminum, chromium, tin, and magnesium, with an aqueous suspension of fumaric acid, and then adding to the resulting mixture a non-oxidizing acid which is capable of reacting with the metal to liberate hydrogen, said non-oxidizing acid being added in at least the amount theoretically required to react with the amount of metal employed, and at such a rate as to avoid substantial liberation of hydrogen gas.

5. -A process for the manufacture of succinic acid, which comprises mixing an aqueous suspension of fumaric acid with a finely divided metal selected from the class consisting of zinc, aluminum, chromium, tin, and magnesium, at a temperature ofabout 85 C. to the boiling point of the mixture, and adding to theresulting mixture a non-oxidizing acid which is capable of reacting with the metal to liberate hydrogen, said non-oxidizing acid being added in at least the amount theoretically required to react with the amount 'of metal employed.

6. A process for the manufacture of succinic acid, which comprises adding to an aqueous suspension. of fumaric acid a finely divided metal selected from thegroup consisting of zinc, alu-' minum, chromium, tin, and magnesium, in ap-'- proximately the amount theoretically required to reduce the fuinaric acid to succinic acid, adding to the resulting mixturea non-oxidizing acid which is capable of reacting with the metal to liberate hydrogen and which is sufliciently stronger than succinic acid to liberate the latter from a su'ccinate of the metal, in approximately the amount theoretically required to react with the amount of metal employed, while maintaining a temperature of 85 6. to the boiling point of the reaction mixture, and recovering osuccinic acid from the resulting reaction mixture.

"I. A- process forthe manufacture of'succinie acid, which comprises adding zinc to an aqueous suspension of fumaric acid, adding a non-oxidizing' mineral acidto the resulting mixture in at least the amount theoretically required to react with the amount of zinc employed While maintaining a temperature of 85 C. to the boiling point of the reaction mixture, and recovering succinic acid from the resulting reaction mixture.

8. A process for the manufacture of succinic acid, which comprises mixing fumaric acid in an aqueous medium with finely divided zinc; adding a non-oxidizing acid at least as strong as formic acid to the resulting mixture, and controlling the rate of said addition and the temperature of the reaction mixture so as to avoid substantial liberation of hydrogen gas.

9. A process for the manufacture of succinic acid, which comprises adding to an aqueous slurry of fumaric acid finely divided zinc in an-amount slightly in excess of that theoretically required to reduce the fumaric acid to succinic acid, then .adding a quantity of sulfuric acid to the resulting mixture inan amount slightly in excess of the chemical equivalent of the zinc employed while maintaining the temperature within the acid, which comprises adding aluminumto an aqueous suspension of fumaric acid, adding a non-oxidizing mineral acid to the resulting mix.- ture in at least the amount theoretically required to react with the amount of aluminum employed while maintaining a temperature of 85 C.,to the boiling point of the reaction mixture, and recovering succinic acid from the resultin reaction mixture.

11. A process for the manufacture of succinic acid, which comprises adding to an aqueous.

slurry of. fumaric acidflnely divided aluminum in an amount slightly in excess of that theoretically'required to reduce the fumaric acid to succinic acid, then adding a quantity of sulfuric acid to'the resulting mixture in an amount slightly in excess of the chemical equivalent of the alumi num employed while maintaining the temperature within the range from to 0., controlling the rate of addition of said acid so as to avoid substantial liberation of hydrogen gas, heating the reaction mixture to a temperature of .to C. to complete the reduction, clarifying the aqueous portion of the reaction mixture, cooling said clarified aqueous portion to effect crystallization of succinic acid, and separating-the crystallized succinic acid from the mother liquor," the amount of water present in said reaction mixture being just enough to form a substantially saturated solution of the succinic acid produced. I f p ELTON B. PUNNETT. 

